The prevalence of asthma varies among communities in the United States. Within New York City (NYC), the reported prevalence of pediatric asthma and hospitalization rates for asthma vary markedly between adjacent neighborhoods. We hypothesize that the difference in the prevalence of asthma observed between neighborhoods in NYC is due to differences in exposure to asthma/allergy environmental triggers (indoor cockroach and mouse allergens, and local sources of diesel particulates), physical activity levels and high body mass index for age. To test this hypothesis, we propose to recruit 800 children age 7 years who reside in NYC and have been enrolled in the HIP health plan through a parent or guardian's employment since birth. The children will be recruited from two types of neighborhoods of approximately equal HIP population size, 1) high asthma prevalence (~16%) neighborhoods [HAPN] 2) lower asthma prevalence (~9%) neighborhoods [LAPN]. Children will be classified as asthmatic or non-asthmatic by telephone administration of the ISAAC survey plus report of asthma controller medication. Employing stratified quota sampling we will recruit an equal number of asthmatics (n=400) and randomly selected non-asthmatics (n=400) enrolled from the combined population of HAPN and LAPN children. The HIPsampling frame will yield a multi-ethnic sample of children from low- middle and middle income homes, all of whom have similar access to health care. We will include measures on SES, ethnicity and built environment in multivariate analyses to control for these potential confounders. This study will use the same measures that are being employed in three other asthma studies being conducted on children the same age who live neighborhoods of high asthma prevalence in NYC. Aim 1. We hypothesize that, compared to children living in LAPN, children living in HAPN will be 1a.) more exposed to cockroach and mouse allergens in the dust and to diesel particulate matter in the air, 1b.) more likely to be sensitized to cockroach and mouse allergens, and 1c.) more sedentary and have a higher body mass index for age. Aim 2. We hypothesize that among children with asthma in LAPN, children with asthma in HAPN will have 2a.) more severe asthma (as classified by symptoms and spirometry), 2b.) higher levels of exhaled nitric oxide, a measure of airway inflammation. Aim 3. We hypothesize that among children sensitized to at least one allergen (i.e., atopic), those who live in a HAPN will be more likely to have asthma than those who live in an LAPN.